1. Technical Field
The present invention relates to a spiral spring employed in a reclining adjustment mechanism provided in a seat frame of a vehicle, specifically relates to a spiral spring formed by spirally forming (coiling into a pitch coiled structure) a band-like steel plate (spring plate member) having high hardness.
2. Background Art
Conventionally, this type (reclining adjustment mechanism) of spiral spring is wound (tightened) when a seat back is tilted backward, and rewound (loosened) to return to an initial shape when the seat back is tilted forward.
However, in a conventional spiral spring, while being wound, there is contact and/or friction and catching between a front surface and a back surface (plate surfaces) facing each other of a spring plate member, and the winding is restricted or stopped at a position where the friction or the catching occurs, or the spiral spring is continuously wound in a distorted condition. In such a condition, spring performance such as correct winding or rewinding cannot be sufficiently exerted, and problems occur such as, the seat back does not tilt, or the seat back does not return to the original position.
To improve such a situation, there are prior documents as follows:
[1] “Spiral spring” of Japanese Unexamined Utility Model Registration Application Publication No. 59-191437. This utility model is characterized in that a concave portion is formed in a coiling direction of a plate member (spring plate member), and the concave portion is sequentially decreased from an inner portion to an outer portion (from the inner end portion to the outer end portion) to reduce the second moment. However, this utility model has problems such as, time and skill is required to manufacture the spiral spring, a dedicated machine is required, and the like.[2] “Spiral spring” of Japanese Unexamined Utility Model Registration Application Publication No. 49-83455. This utility model is characterized in that, in a coiling direction of a plate material (spring plate member), ridges are formed on a front surface and/or a back surface (a single surface or both surfaces), and an area between the ridges is used to retain lubricant, so that, by the lubricant, abnormal noise is prevented from occurring and durability is improved. However, this utility model has a structure in which many grooves are formed, so that it cannot be considered to form the spiral spring by cold rolling (material is difficult to move). In addition, this utility model does not disclose a pitch coiled structure which is best suited to a reclining adjustment mechanism and in which a gap between an outer spring plate member and an intermediate spring plate member and a gap between the intermediate spring plate member and an inner spring plate member are adjusted. This is a usual spiral spring and it is considered that this spiral spring has a problem when being used as a spiral spring for a vehicle described below.[3] “Spiral spring” of Japanese Unexamined Patent Application Publication No. 55-44174. This invention is characterized in that a cross-section of the spring plate has a circular arc shape, so that material is saved and the spring is lightened. However, this invention does not disclose a pitch coiled structure, so that it is considered that this invention has the same problem as in document [2].[4] “Spiral spring” of Japanese Unexamined Patent Application Publication No. 9-257070. This invention is characterized in that the inner portion (coiled center) and the outer portion (circumferential portion) of the spiral spring are divided by a line, a gap between the spring plates of the outer portion or the inner portion whose diameter is large is set to be larger than a gap between the spring plates of the outer portion or the inner portion whose diameter is small when the spring is in a free state, and the spring plates are not in contact with each other (friction is set to be substantially 0) when the spring is tightened, so that spring performance is exerted and fatigue is reduced. However, it is considered that the simple structure of this invention in which the inner portion and the outer portion are divided by a line cannot sufficiently cope with a reclining adjustment mechanism in which complex movement of a vehicle and/or an applied load vary.[5] “Spiral spring” of Japanese Unexamined Patent Application Publication No. 2003-148533. This invention has a structure in which, in a spiral spring formed by spirally forming a band-like steel plate having high hardness, shapes of surfaces of steel plates facing each other are differentiated from each other (a structure in which projection is provided on plate surfaces facing each other). This invention is characterized in that spring performance is achieved while reducing a contact area between the plate surfaces facing each other and avoiding catching when the spiral spring is being wound. However, this invention does not sufficiently disclose a pitch coiled structure, so that it is considered that this invention has the same problem as in document [2].[6] “Spiral spring structure” of Japanese Unexamined Patent Application Publication No. 2006-177385. This invention is a spring which can be formed by a surface compaction roller, and this invention is characterized in that a pair of ridges are continuously formed on both ends in a direction perpendicular to a coiling direction of the spring, and the spring is used as a source of power or used for a reclining adjustment mechanism. However, this invention does not sufficiently disclose a pitch coiled structure, so that it is considered that this invention has the same problem as in document [2].
The utility models and the inventions in the above-described documents [1] to [6] do not sufficiently disclose a pitch coiled structure best suited to a reclining adjustment mechanism, so that further improvements and innovations are required. In particular, the utility models and the inventions in the above-described documents [1] to [6] do not have a means for solving a problem related to the returning speed of the spring and/or the reclining seat, so that it is considered that the utility models and the inventions are not suited to this type of reclining adjustment mechanism.